858 research outputs found
Pulsed high-power arc heater with improved cathode and triggering mechanism
System employs pulsed, constricted arc heater capable of multi-MW power, permitting quasi-stationary flow conditions during latter half of pulse of about 5 msec. System description is given
Signatures of spin in the n=1/3 Fractional Quantum Hall Effect
The activation gap Delta of the fractional quantum Hall state at constant
filling n =1/3 is measured in wide range of perpendicular magnetic field B.
Despite the full spin polarization of the incompressible ground state, we
observe a sharp crossover between a low-field linear dependence of Delta on B
associated to spin texture excitations and a Coulomb-like behavior at large B.
From the global gap-reduction we get information about the mobility edges in
the fractional quantum Hall regime.Comment: 4 pages, 3 figure
Myxobolus aeglefini in Wittlingen (Merlangius merlangus)der Nordsee und der lrischen See
In June 1994 and 1995 stations in the North, Irish, Celtic Seas and the Channel were studied for the occurrence of Myxobolus aeglefini in whiting (Merlangius merlangus). The disease was visible externally as either white nodules of
a few millimeters diameter in the upper mouth cavity, gill arches and the basis of pelvic fins and in severe cases also on the lower jaws or in the cornea and sclera of the eye. It was verified morphometrically in histological sections of infected eyes by size and shape of spores. Myxobolus aeglefini was present in low prevalences at two North Sea stations and high prevalences of up to 49 % in the Irish Sea (Solway Firth) during both cruises. Whiting
between 23 and 55 cm were found to be infected. Neither length-age prevalences nor condition factors and gonado, spleen, liver somatic indices differed in diseased and healthy fishes
Social interaction, noise and antibiotic-mediated switches in the intestinal microbiota
The intestinal microbiota plays important roles in digestion and resistance
against entero-pathogens. As with other ecosystems, its species composition is
resilient against small disturbances but strong perturbations such as
antibiotics can affect the consortium dramatically. Antibiotic cessation does
not necessarily restore pre-treatment conditions and disturbed microbiota are
often susceptible to pathogen invasion. Here we propose a mathematical model to
explain how antibiotic-mediated switches in the microbiota composition can
result from simple social interactions between antibiotic-tolerant and
antibiotic-sensitive bacterial groups. We build a two-species (e.g. two
functional-groups) model and identify regions of domination by
antibiotic-sensitive or antibiotic-tolerant bacteria, as well as a region of
multistability where domination by either group is possible. Using a new
framework that we derived from statistical physics, we calculate the duration
of each microbiota composition state. This is shown to depend on the balance
between random fluctuations in the bacterial densities and the strength of
microbial interactions. The singular value decomposition of recent metagenomic
data confirms our assumption of grouping microbes as antibiotic-tolerant or
antibiotic-sensitive in response to a single antibiotic. Our methodology can be
extended to multiple bacterial groups and thus it provides an ecological
formalism to help interpret the present surge in microbiome data.Comment: 20 pages, 5 figures accepted for publication in Plos Comp Bio.
Supplementary video and information availabl
Spectral properties of rotating electrons in quantum dots and their relation to quantum Hall liquids
The exact diagonalization technique is used to study many-particle properties
of interacting electrons with spin, confined in a two-dimensional harmonic
potential. The single-particle basis is limited to the lowest Landau level. The
results are analyzed as a function of the total angular momentum of the system.
Only at angular momenta corresponding to the filling factors 1, 1/3, 1/5 etc.
the system is fully polarized. The lowest energy states exhibit spin-waves,
domains, and localization, depending on the angular momentum. Vortices exist
only at excited polarized states. The high angular momentum limit shows
localization of electrons and separation of the charge and spin excitations.Comment: 14 pages 18 figure
Microfield Dynamics of Black Holes
The microcanonical treatment of black holes as opposed to the canonical
formulation is reviewed and some major differences are displayed. In particular
the decay rates are compared in the two different pictures.Comment: 22 pages, 4 figures, Revtex, Minor change in forma
Matrix Theory Description of Schwarzschild Black Holes in the Regime N >> S
We study the description of Schwarzschild black holes, of entropy S, within
matrix theory in the regime . We obtain the most general matrix
theory equation of state by requiring that black holes admit a description
within this theory. It has a recognisable form in various cases. In some cases
a D dimensional black hole can plausibly be thought of as a
dimensional black hole, described by another auxiliary matrix theory, but in
its regime. We find what appears to be a matrix theory
generalisation to higher dynamical branes of the normalisation of dynamical
string tension, seen in other contexts. We discuss a further possible
generalisation of the matrix theory equation of state. In a special case, it is
governed by dynamical degrees of freedom.Comment: 22 pages. Latex fil
A Selective, Efficient and Environmentally Friendly Method for the Oxidative Cleavage of Glycols
A catalytic methodology for the oxidative cleavage of vicinal diols is described as an advantageous alternative in terms of the environmental impact on classical methods involving toxic oxidants. The novel strategy is based on the use of dioxomolybdenum(VI) complexes as catalysts and dimethyl sulfoxide (DMSO) as an oxidant and displays high selectivity and a broad scope for glycol cleavage. In addition, the developed system is also useful for the oxidation of acyloins to diketones.Ministerio de Economía y Competitividad
(MINECO) and FEDER (CTQ2013-48937-C2-1-P) and Junta
de Castilla y León (BU237U13
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